The Cassini Live Update Process

Abstract

The Cassini orbiter is an international science mission to the Saturnian system with 12 science instruments onboard. The Cassini spacecraft lacks a scan platform, which means the entire spacecraft must be rotated to control pointing of any one instrument's boresight. The resulting complex sequences of commands are built beginning many months before execution onboard. Late ephemeris updates from improved navigation data (i.e. after an orbital trim maneuver) often result in pointing commands in the sequence no longer being accurate enough to obtain the desired science observation. This paper will provide an overview of how Cassini uses live updates to address this potential loss of data, including the software developed for this process.